Nguyen Phuoc Quy Thang, Watanabe Yuta, Matsui Hidenori, Sakata Nanami, Noutoshi Yoshiteru, Toyoda Kazuhiro, Ichinose Yuki
The Graduate School of Environmental, Life, Natural Science and Technology, Okayama University.
Microbes Environ. 2025;40(3). doi: 10.1264/jsme2.ME25019.
Chemotaxis is essential for infection by plant pathogenic bacteria. The causal agent of tobacco wildfire disease, Pseudomonas syringae pv. tabaci 6605 (Pta6605), is known to cause severe leaf disease and is highly motile. The requirement of chemotaxis for infection has been demonstrated through the inoculation of mutant strains lacking chemotaxis sensory component proteins. Pta6605 possesses 54 genes that encode chemoreceptors (known as methyl-accepting chemotaxis proteins, MCPs). Chemoreceptors are classified into several groups based on the type and localization of ligand-binding domains (LBD). Cache LBD-type chemoreceptors have been reported to recognize formate in several bacterial species. In the present study, we identified Cache_3 Cache_2 LBD-type Mcp26 encoded by Pta6605_RS00335 as a chemoreceptor for formate using a quantitative capillary assay, and named it McpF. Although the deletion mutant of mcpF (ΔmcpF) retained attraction to 1% yeast extract, its chemotactic response to formate was markedly reduced. Swimming and swarming motilities were also impaired in the mutant. To investigate the effects of McpF on bacterial virulence, we conducted inoculations on tobacco plants using several methods. The ΔmcpF mutant exhibited weaker virulence in flood and spray assays than wild-type and complemented strains, highlighting not only the involvement of McpF in formate recognition, but also its critical role in leaf entry during the early stages of infection.
趋化作用对于植物致病细菌的感染至关重要。烟草野火病的病原菌丁香假单胞菌烟草致病变种6605（Pta6605），已知会引发严重的叶片病害，且具有高度运动性。通过接种缺乏趋化感应成分蛋白的突变菌株，已证明趋化作用对感染的必要性。Pta6605拥有54个编码化学感受器（称为甲基接受趋化蛋白，MCPs）的基因。化学感受器根据配体结合结构域（LBD）的类型和定位分为几个组。据报道，在几种细菌物种中，Cache LBD型化学感受器可识别甲酸。在本研究中，我们使用定量毛细管分析法将由Pta6605_RS00335编码的Cache_3 Cache_2 LBD型Mcp26鉴定为甲酸的化学感受器，并将其命名为McpF。尽管mcpF的缺失突变体（ΔmcpF）对1%酵母提取物仍保持吸引力，但其对甲酸的趋化反应明显降低。该突变体的游动和群游运动能力也受损。为了研究McpF对细菌毒力的影响，我们使用几种方法对烟草植株进行了接种。在水淹和喷雾试验中，ΔmcpF突变体表现出比野生型和互补菌株更弱的毒力，这不仅突出了McpF参与甲酸识别，还表明其在感染早期叶片侵入过程中的关键作用。
